8th Maths : Chapter 4 : Life Mathematics : Summary

**SUMMARY**

• When the S.P is more than
the C.P, then there is a gain or profit. *Profit/Gain =S.P – C.P.*

• When the S.P is less than the C.P, then
there is a loss. *Loss = C.P – S.P.*

• The profit or loss is always calculated
on the cost price.

• Selling price = Marked price – Discount.

• **Formulae**

• When the interest is compounded annually
but rate of interest differs year by year, where a, b and c are interest
rates for the I, II and III years respectively.

• When interest is compounded annually
but time period is in fraction say a *b/c*
years,

• C.I = A−P (Amount − Principal).

• The simple interest and the compound
interest remains the same for the first year or the first conversion period.

• For 2 years, the difference in C.I and
S.I is C.I − S.I =P (r/100)^{2}.

• For 3 years, the difference in C.I and
S.I is C.I − S.I = .

• *x *and* y *are said to vary
directly if **y
= k x**

• *x *and* y *are said to vary inversely, if *xy* =* k** *always, where* k *is called the proportionality constant and* k *> 0.

• There will be problems which involve
a chain of two or more variations in them. This is called as compound variation.

• By finding the proportion, we can use
the fact that the product of the extremes is equal to the product of the means to
find the unknown (*x*) in the problem.

• By using the formula = [ P_{1}×D_{1}×H_{1}
] / W_{1} = [ P_{2}×D_{2}×H_{2} ] / W_{2},
we can find the unknown (*x*).

• We can also find the unknown (x) by Multiplicative
Factor Method.

• If two persons X and Y can complete some
work individually in ** a**
and

** **

__ICT CORNER__

**Step-1** Open the Browser type the URL Link given
below (or) Scan the QR Code. GeoGebra work book named “LIFE MATHEMATICS” will open.
Click on the worksheet named “Percentage”.

**Step-2** In the given worksheet you can drag
the red points E and F to change the Blue rectangle. Find the ratio of Blue with
the whole by counting the squares and check the ratio and percentage.

*Go through the remaining worksheets given for this chapter*

**Browse in the link**

Life Mathematics:

https://www.geogebra.org/m/fqxbd7rz#chapter/409575
or Scan the QR Code.

*Pictures
are indicatives only.

*If browser
requires, allow Flash Player or Java Script to load the page.

** **

__ICT CORNER__

**Step-1 **Open the Browser type the URL Link given
below (or) Scan the QR Code. GeoGebra work sheet named “8th Standard III term” will
open. Select the work sheet named “Work Day Problem”

**Step-2** Click on “ NEW PROBLEM”. Check the calculation
and work out yourself.

**Browse in the link**

Life Mathematics:

https://www.geogebra.org/m/xmm5kj9r
or Scan the QR Code.

Tags : Life Mathematics | Chapter 4 | 8th Maths , 8th Maths : Chapter 4 : Life Mathematics

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8th Maths : Chapter 4 : Life Mathematics : Summary | Life Mathematics | Chapter 4 | 8th Maths

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